Protective system



1 mg. I4, 1934. P, D. ANDREWS PROTECTIVE SYSTEM Filed June 23; 1930 Invent or Pau I D. Andrews,

His Attorney.

Patented Aug. I4, 1934 UNITED STATES PATENT orrrcs 1,970,411 I raoTEcrIvEsYsT M Paul I). Andrews, Schenectady, N. Y., assignor to General Electric "Company, a corporation of Ncw-York My invention relates to protective systems for electron discharge devices and it has for one of its objects to provide an improved method and means for protecting electron discharge devices against excessive heating. g

in the operation of hi h frequency signaling systems, particularly onboard ship, circuit faults frequently occun occasioning excessive heating of the electron discharge "evices which are employed the system. Thus, for example, it frequently happens thatthe antenna of a radio transmitting system becomes grounded, or short circuited, or is otherwise destroyed by waves, in battle. In case of a fault of this nature the anodes of the discharge devices employed in the latter stage, or stages, of the power amplitying equipment of the transmitter may be subjected to very rapid heating and are likely to be injured or destroyed within a very short period unless protective means are provided to care for the emergency.

One of the objects of my invention is to provide a method and means whereby somewhat more complete and satisfactory protection may e applied to the discharge device than has here- 136E018 been possible.

A further object or" the invention is to provide means responsive to the heating of the discharge device itself, and which operates practically simultaneously with the rise of temperature to a predetermined dangerous egree to control the circuits of the discharge device and thereby protect it from injury.

A further object of the luv ntion is to provide means having the above characteristics and which operates in response to heatradiated from the heated electrode, or electrodes, of the discharge device.

The novel features which I believe to be characteristic of my invention are set forth with par-- ticular'ty in the appended claims. My invention itself however, both as to its organization and other suitablesource, conventionally indicated I in the drawing at 5, are supplied through input transformer 6 to the grid of the discharge device.

The output circuit of the discharge device includes a tuned circuit '7 which is connected between the anode and cathode of the discharge device and is coupled to an antenna circuit 8. Anode potential for the discharge device is supplied from a resistance 9 and bias potential for the grid thereof is supplied from a resistance 10, these resistances being connected in series and constituting a potentiometer connected across a source of potential 11, the cathode of the discharge device being connected at a point between thetwo resistances. he potential upon the resistance 10 is normally of sufiicient magnitude to cause the grid to be sufficiently negative with respect to the cathode substantially to preclude the flow of electrons from the cathode to the .anode.

This potential, therefore, normally interrupts operation of the discharge device.

Inorder to transmit the high frequency oscillations in accordance with desired signals, a key 12 is employed to control a suitable keying relay 13, the contacts of which are connected in shunt with t to resistance 10. Thus upon operation of the key, the relay 13 short circuits the resistance 10 and thereby removes the bias potential from the grid of the discharge device and renders it operative to amplify high frequency oscillations from the source 5.

It will be readily understood by one skilled in the art that if the antenna circuit 8 becomes short circuited, and, likewise, if certain other faults occur in the circuit, the discharge device is subject to excessive heating. In accordance with my invention this excessive heating is prevented by providing a suitable radiation pyrometer indicated in the drawing at 14 to, control the energizing circuits of the discharge device. This pyrorneter may comprise any suitable thermocouple or junctionor" dissimilar metals such as tellurium and constantan, for example, whereby an electrornotive force is generated having a;

magnitude dependent upon the temperature of the junction. This thermo-electric generator, or thermocouple, is connected in circuit with the winding of a sensitive relay 15.

Therelay 15 and thermocouple 14 are shown 4; as arranged within a suitable housing indicated by the rectangle 17 located in proximity to the discharge device. The housing has a lens 16 arranged therein for the purpose of focusing heat from the anode of the discharge device 1,;

impulses by means of the system theoperator operates the key 12 in accordance with a tele-- graphic code, thereby causingoscillations to be transmitted from the antenna when the key is closed. Under these conditions the electromotive force generated by the thermo-electric generator 14 is insuficient to cause operation of the relay 15. If, however, during the transmission of sig nal impulses, due to a fault occurring in the circuit or due toany other cause, such as holding the key 12 closed for an abnormally long period, excessive heating of the discharge device is caused, the electromotive force generated by the thermo-electric generator is will be suificient to cause operation of the relay 15. This relay will then open its contacts and thereby deenergize relay 13 and cause the negative bias to again be applied to the grid of the discharge device, thereby reducing the anode current and protecting the device against injury due to the fault.

It will thus be seen that the supply of energy to the discharge device, in accordance with my invention, is reduced substantially simultaneously with the excessive heating thereof. This characteristic of the device is ofv great'importance since after a certain predetermined dangerously high temperature is reached, which is likely to occur due to faults of the type indicated, either the electrodes, or the seal of the discharge device, or both, are likely to be destroyed within a very short period. The relay 15 in accordance with my invention may be adjusted to operate practically instantaneoulsy upon such a predetermined temperature being attained.

While I have described my invention as applied particularly to anelectron discharge device employed in a radio signaling system, it will of course be understood that it isnot limited thereto but that it may be applied to the protection of electron discharge devices as generally applied. Further, while I have shown a particular means whereby the energizing circuits of the transmitter are controlled in response to the thermo-electric generator 14, it will of course be understood that this is by way of illustration of a preferred embodiment of my inventionand that any suitable means whereby the energy supplied tothe discharge device is materially reduced in response to the electromotive force of the thermo-electric generator may be employed; It will thus be understood 1 that while I have disclosed but a single embodiment of my invention, I do not wish to be limited thereto since many modifications may be made, and that I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an electron discharge device subject to excessive heating during operation thereof, a thermo-electric generator subject to heat radiated from an electrode of said discharge device, and means operable responsively to 'electromotive force generated by said thermoelectric generator to control a circuit of said electron discharge device.

2. In combination, an electron discharge device'having an electrode subject to excessive heating, a thermo-electric generator, means for focusing heat radiated from said electrode upon said generator whereby an electromotive force is produced in accordance with the heating of said electrode, an energizing circuit for said discharge device, and means responsive to electromotive force generated by said thermo-electric generator for controlling said energizing circuit.

3. The combination, in a signal system, of an electron discharge device having an element which is subject to excessive heating during operation of said system, means for generating an electromotive force in accordance with the heating of said element, means including a keying circuit for controlling the operation of said discharge device in accordance with desired impulses, and means responsive'to said electro- He motive force for controlling said keying circuit thereby to render said discharge device inopera- 4. In combination, an electron discharge device subject to excessive heating when energized,

a thermo-electric generator comprising dissimilar metals in contact with each other, said thermo-electric generator being arranged for substantially instantaneous response to heating of an electrode of said discharge device, and

means responsive to electromotive force produced between the dissimilar metals of said generator to control the energization of said electron discharge device.

5. In combination, an electron discharge detromotive force generated between said metals to control said connections thereby to protect said discharge device against variations in said impedance.

PAUL D. ANDREWS. 

